The present invention relates to recovery of reusable component materials from waste construction materials, and particularly relates to a method and apparatus for economical recovery of paper and gypsum from waste plasterboard.
Plasterboard is commonly used for covering the framework of interior walls of buildings and commonly includes a cover sheet of paper or other tough fibrous material adhered to at least one major side of a planar core of a hardened cast mineral material such as, typically, plaster of paris, a cast gypsum material. As used herein, the term "plasterboard" is to be taken generally to include various types panel of material of this general type of construction, and the term "gypsum" will be used to refer generally to the cast core of mineral material of such plasterboard.
Quantities of waste plasterboard are usually left over after construction of new buildings or remodeling of old buildings. Such waste plasterboard is a nuisance to construction contractors who are eager to dispose of the material without having to pay for having it hauled to landfill sites. In the form of odd-sized pieces the plasterboard is bulky, and it takes up considerable amounts of space if discarded into landfill. The material is not easily disposed of, since it is relatively heavy and not particularly easy to handle. However, plasterboard contains both paper or similar material and gypsum, both of which can be reused if separated from each other. However, the gypsum normally adheres tightly to the paper, making it difficult to separate the paper from the gypsum core material. Previously, hammer mills and other grinding or shredding equipment have been used to break the plasterboard into small pieces and free the gypsum from the paper thereof. This, however, produces pieces of paper too small to be baled conveniently to be transported for recycling of the paper fiber. The smallest pieces of paper thus produced are also impractical to remove from the resultant gypsum and make the gypsum undesirable for certain uses. For example, powdered gypsum is very useful as a soil treatment, particularly in culture of mushrooms, but the inclusion of paper bits with the gypsum makes the gypsum undesirable for such use. Additionally, the use of a hammer mill produces undesirably large quantities of dust.
What is needed, then, is a method and apparatus for separating the paper or similar sheet material used as cover layers from the gypsum core of plasterboard, so that both the paper and gypsum materials can be reused, instead of the plasterboard having to be discarded as landfill material.